If WotC does reprint settings, which versions should they pick? The determining factors, IMO, are going to be demand, attractiveness to fans, and production costs. The last factor means that, IMO, we're likely to see a preference for hardcovers or for boxed sets repackaged as hardcover volumes. WotC has done the latter once already with Council of Wyrms. And Birthright almost got the same treatment before it was canned; I don't know if the hardcover planned for Summer 1998 was going to be a repackaging or a true 2nd Edition. I wonder if the files still exist anywhere.
The Realms are going to be the big problem in this regard--the Grey Box, the Revised Box and the 3E version all have their adherents, AFAIK. Of course, between the 4E book and the forthcoming "Elminster Presents Ed Greenwood's Realms", they might see no point.
Dragonlance . . . the 3.5 version is still available cheap used, and Tales of the Lance was not well received and includes a whole lot of physical fiddly bits that wouldn't convert well and would probably be too expensive to reproduce. DRAGONLANCE Adventures would work as something that fans like and could be done inexpensively, but it's really an appendage to the original modules and a sourcebook for the Legends novels. A reprint of the Dragonlance Classics compilations might be workable, though.
Dark Sun was done recently for 4E and is difficult to convert from boxed to book, AFAIK.
Greyhawk? The 80s folio is pretty much the only option for the nostalgia market, unless the Living Greyhawk Gazetteer had a much bigger following than I've heard about.
Planescape . . . I'm not familiar with the way the boxed set is laid out, but could it be combined into a hardcover and separate map pack without too much loss of cohesion?
Ravenloft already has a well-received hardcover in Domains of Dread; the 3E version is also hardcover, but suffers from the decision to spin off "DMs only" material into a supplement.
